In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of pattern miniaturization. Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter (energy higher) than these excimer lasers, such as EB (electron beam), extreme ultraviolet radiation (EUV), and X ray.
As shortening the wavelength of the exposure light source progresses, resist materials for use with these types of exposure light sources require improvement in lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources. As a resist material that satisfies these conditions, a chemically amplified resist composition is known,
For example, in the case where the developing solution is an alkali developing solution (alkali developing process), a chemically amplified resist composition which contains, as a base component (base resin), a resin which exhibits increased solubility in an alkali developing solution under action of acid, and an acid generator is typically used. If the resist film formed using the chemically amplified resist composition is selectively exposed during formation of a resist pattern, then within the exposed portions, acid is generated from the acid-generator component, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution. In this manner, the unexposed portions remain to form a positive resist pattern.
The base resin used exhibits increased polarity by the action of acid, thereby exhibiting increased solubility in an alkali developing solution, whereas the solubility in an organic solvent is decreased. Therefore, when such a base resin is applied to a process using a developing solution containing an organic solvent (organic developing solution) (hereafter, this process is referred to as “solvent developing process” or “negative tone-developing process”) instead of an alkali developing process, the solubility of the exposed portions of the resist film in an organic developing solution is decreased. As a result, the unexposed portions are dissolved and removed by the organic developing solution, and a negative pattern in which the exposed portions remain is formed. The negative tone-developing process is proposed, for example, in Patent Document 1.
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are now used as base resins for chemically amplified resist compositions that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 2).
Here, the term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position. The term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position.
Furthermore, currently, in addition to the base resin and the acid generator, a nitrogen-containing organic compound such as an alkylamine, an alkylalcoholamine or the like is added to chemically amplified resist compositions (for example, see Patent Documents 3 and 4). The nitrogen-containing organic compound functions as a quencher which traps the acid generated from the acid generator, and contributes to improving various lithography properties such as a pattern shape and the like.